This invention relates to the field of designing and constructing filter cartridges used in filters for fluids flowing in hydraulic motors or apparatuses.
In general, such filter cartridges are shaped cylindrically and are composed of a filter medium, that can be made e.g. of paper, cardboard or else felt, to which two end flanges are joined. The present trend is to make such filter cartridges from materials that can be incinerated. In particular, regarding flanges, the present trend is to make plastic flanges.
Such filter cartridges are installed inside filter feed troughs, and in many instances, so as to cooperate with a center tube thereof. This center tube can consist of one or two pieces. In order to ensure sealing during filtration, plastic sealing rings are arranged between center tube and flanges.
State-of-the-art gaskets are installed under compression in order to operate correctly. However, though such compression poses no problem for metal parts, it has turned out that it could eventually result in sealing damage when using plastic flanges.
It is the main object of this invention to provide sealing means for filter cartridges without this drawback and therefore allowing to ensure good sealing even with plastic parts.
In particular, it is an object of this invention to reveal such means that allow of an adaptation to dimensional evolution between the end flange and the center tube of the trough.
The various objects are achieved with the invention relating to a filter cartridge to be inserted in the filter feed trough of a filter for fluid flowing in a hydraulic motor or apparatus and for cooperating with a center tube of said filter, said cartridge having a filter medium and at least one end flange joined to said filter medium, characterized in that said end flange is extended by a projecting part defining a cavity for lodging a gasket and in that said gasket has at least one pressurizing duct inside said cavity.
Such a pressurizing duct inside the cavity allows to press the gasket against the center tube during filter operation and thus to provide perfect sealing, whatever the evolution of clearance between flange and tube may have been. The gasket can be installed with low initial compression (it will be noted that initial compression is independent of gasket performance) and the gasket can function at high pressures.
It will be understood that the pressurizing duct can be produced in different ways inside the end flange. According to a preferred alternative, this duct consists of a plurality of notches, advantageously distributed equally over the inside flange rim.
The cavity mentioned above for lodging the gasket can also be produced in several ways. In particular, this cavity has the advantage of making it easier to pull out the gasket together with the filter. According to a particularly interesting alternative, said projecting part includes a first round portion essentially parallel to the longitudinal axis of said cartridge extended by at least one second portion essentially perpendicular to said first portion. It will be understood that, in this embodiment, the first and second portions are formed integrally. The cavity thus defined will permit easy prepositioning of the gasket inside the trough without letting it come out easily. Such prepositioning will make the installation of the cartridge and gasket assembly easier. This cavity will also allow to pull out easily the filter/gasket assembly from the trough, without the risk of the gasket staying inside the trough.
Although the second portion of the projecting part defining the cavity can be continuous for the whole circumference of the first portion, according to a preferred alternative, this second portion will consist of a plurality of pins advantageously distributed equally over the circumference of the first round portion.
According to another alternative, the cavity can also be defined by a first round portion essentially parallel to the longitudinal cartridge axis, on the one hand, and a round member that can be joined, e.g. through welding, in particular ultrasonic welding, engagement or any other means, to the round portion under consideration, on the other hand. In certain embodiments, such a round member may have at least one opening.
The invention also relates to an assembly composed of a filter cartridge such as defined above and a gasket having at least three lobes defining at least three fluid receiving areas.
According to an alternative, this gasket may be essentially h or l-shaped in cross-section, i.e. have three lobes.
According to another preferred alternative of the invention, this filter gasket will have at least four lobes. According a most preferred alternative, it will be essentially x-shaped in cross-section.